chore(ci): update cachix/install-nix-action digest to 2126ae7

Author: renovate[bot]

.github/workflows/ci.yml

@@ -28,7 +28,7 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
-      - uses: cachix/install-nix-action@fd24c48048070c1be9acd18c9d369a83f0fe94d7 # v31
+      - uses: cachix/install-nix-action@2126ae7fc54c9df00dd18f7f18754393182c73cd # v31
         with:
           github_access_token: ${{ secrets.GITHUB_TOKEN }}